Automation, at least from the point of view of the plant construction firm, can be seen as a contest of questions on strength of materials on the one hand, and, on the other hand, the rapidity of the progression of movement. In the present case, however, direct influence can be applied only to one part of the plant elements. For example, practically no influence can be exerted on bag materials in the realm of the food and feed industry, since these (bag materials) are essentially specified by the market. A stronger paper quality results practically automatically in greater expenditures for the clients, since we are dealing with mass goods, and savings by further increasing automation is questionable. A further central problem in the case of automation of the bagging process lies with the bag itself.
In contrast to piece goods, such as boxes or finished products, such as chocolates or automobile components, a bag, particularly in the filled condition, offers a constant external form and external dimensions only within wide limits. Another problem is a certain disproportionality between the plant elements, consisting today principally of steel, and the bag material which may be paper, plastic or textile fabric. Anyone who has carried around by hand paper or plastic bags weighing from 30-50 kg or more already consciously recognizes the problem of the relationship: weight of the bag and strength of the bag jacket. It is further a fact from experience that sources of disturbance can be eliminated almost without effort by manual intervention in the case of semi-automatic plants, this by means of a slight straightening up of the bag, better raising the bag, orderly preparation of the open end of a filled paper bag, etc. Any average person possesses, in this respect, a broadly considered sense concerning any technique. The semi-automatic filling of bags, however, is rejected by many since there is quite often associated with this still considerable physical exertion, and this on a schedule that is dictated by the machine. This applies particularly if the bags display 50 kg and more. Here also, within the scope of solutions known up until now, automation has a "natural" upper limit.
The invention would also provide as a partial task improvement in the manipulation of bags for bagging and closing the transport bags.
In the case of one known state of the art solution, the problem of closing bags of different heights is resolved by the fact that the continuous conveyor, most often an endless conveyor belt about a point of rotation, is adaptable in raisable and lowerable fashion on the delivery side, respectively on the loading side, to the various bag heights. Hence, free-fall of the bag can be prevented at both transfer points. This solution has proven itself in practice. In particular, balancing mechanisms and other sources of disturbance can be avoided in this fashion.
Therefore, also one of the principal tasks of the invention, in the case of solutions with continuous conveyors and/or conveyor belts that are adjustable in inclination, therefore also without free-fall of the bags and/or corresponding auxiliary means for avoiding same, was to close the bags in trouble-free fashion and cleanly, e.g. to stitch cleanly. The solution in accordance with the invention is characterized by the fact that the movements of the closing tools are initiated harmoniously in synchronism with the movement of the bag and/or its range of opening.
The task has been resolved by the fact that the individual phases of the closure operation are carried out harmoniously with the conveying movement of the bags on a continuously running conveyor belt.
With the knowledge from the invention, the previous path to automation of bag closure can now, looking back, be judged as a false path. Up to certain limits, using the so-called "speed trick", movements running counter to each other can be coupled together, provided at least that one of the movements is executed sufficiently slowly and the other movement sufficiently rapidly. The logic alone included in this leads to a natural limit of increasing speed.
The invention further permits various advantageous other embodiments. In a particularly preferred solution, the spreading tools execute, during the spreading movement, a movement that follows the range of bag opening. It is precisely through the second movement of the means for spreading the open, top end of a freshly filled bag, superimposed and added to the first movement of the transport motion, that the spreading movement can now be carried out more slowly. In spite of an increase of the overall speed run, this leads to a much slower, more careful and, therewith, more guarded spreading movement of the bag end.
It is particularly advantageous if the spreading tools are moved, during the spreading movement, on the average, with the same speed and in the same direction as the open bag ends. The importance of this in itself simple procedure in accordance with the invention is recognized by the fact that the bag can be stitched only as well as it has been prepared for this. Spreading of the bag end, present in round or oval form after filling, into a corresponding, long flat form for the sewing machine, is the preparatory step for stitching and, therewith, for the positive and orderly closure of the bag for all further manipulations, particularly for subsequent transport loading. The same would also apply in the case of gluing.
A slow movement always had the advantage of being able to be determined optically and also to be corrected in practice. It is further particularly advantageous if the movement is carried out by means of pneumatically driven spreading tools. The pneumatic pressure can be set to a predetermined maximum pressure. Hence, it requires no stop. Hence, tolerances in opening width of the bag plays no role in the slow movement. The spreading tool always adapts itself.
The idea of the invention can be applied in particularly elegant fashion with the measure already being used by the applicant, by adjusting the inclination of the belt such that variations in the height of the bag are compensated by corresponding one-sided adjustment in height of the receiving side of the belt, with a slight rotational movement being executed about an axis in the region of discharge from the belt.